Design of tunable protein-releasing nanoapatite/hydrogel scaffolds for hard tissue engineering

Hierarchically structured porous scaffolds based on nanocrystalline carbonated hydroxyapatite reinforced hydrogels (Gellan or Agarose) have been tested as protein release matrices while evaluation their in vitro biocompatibility. The shaping method used develops under mild conditions thus allowing the incorporation of labile substances. The Bovine Serum Albumin (BSA), employed as a model protein, has been included by using two drug-inclusion strategies: during the scaffolds preparation (in situ process) or by injection of an aqueous protein solution within (ex situ process). The release studies showed a more controlled BSA delivery when the protein was incorporated during the scaffold preparation when compared to that where the protein has been loaded in a second step (ex situ process). The release patterns can also be tailored as a function of the scaffold composition (ceramic/polysaccharide ratio and nature) as well as the drying technology employed. Biocompatibility studies demonstrated that these scaffolds, regardless of the composition, allow the culture of osteoblasts on and around the material, thus supporting the potential use of these biomaterials for bone tissue engineering.     

Effects of LP-MOCVD prepared TiO2 thin films on the in vitro behavior of gingival fibroblasts

We report on the in vitro response of human gingival fibroblasts (HGF-1 cell line) to various thin films of titanium dioxide (TiO₂) deposited on titanium (Ti) substrates by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The aim was to study the influence of film structural parameters on the cell behavior comparatively with a native-oxide covered titanium specimen, this objective being topical and interesting for materials applications in implantology. HGF-1 cells were cultured on three LP-MOCVD prepared thin films of TiO₂ differentiated by their thickness, roughness, transversal morphology, allotropic composition and wettability, and on a native-oxide covered Ti substrate. Besides traditional tests of cell viability and morphology, the biocompatibility of these materials was evaluated by fibronectin immunostaining, assessment of cell proliferation status and the zymographic evaluation of gelatinolytic activities specific to matrix metalloproteinases secreted by cells grown in contact with studied specimens. The analyzed surfaces proved to influence fibronectin fibril assembly, cell proliferation and capacity to degrade extracellular matrix without considerably affecting cell viability and morphology. The MOCVD of TiO₂ proved effective in positively modifying titanium surface for medical applications. Surface properties playing a crucial role for cell behavior were the wettability and, secondarily, the roughness, HGF-1 cells preferring a moderately rough and wettable TiO₂ coating.     

Structural,chemical surface and transport modifications of regenerated cellulose dense membranes due to low-dose γ-radiation

Modifications caused in commercial dense regenerated cellulose (RC) flat membranes by low-dose γ-irradiation (average photons energy of 1.23 MeV) are studied. Slight structural, chemical and morphological surface changes due to irradiation in three films with different RC content were determined by ATR-FTIR, XRD, XPS and AFM. Also, the alteration of their mechanical elasticity has been studied. Modification of membrane performance was determined from solute diffusion coefficient and effective membrane fixed charge concentration obtained from NaCl diffusion measurements. Induced structural changes defining new and effective fracture propagation directions are considered to be responsible for the increase of fragility of irradiated RC membranes. The same structural changes are proposed to explain the reduction of the membrane ion permeability through a mechanism involving either ion pathways elongation and/or blocking.     

Preparation and properties of chitosan nanocomposite films reinforced by poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) treated carbon nanotubes

Carbon nanotube-based nanocomposites of chitosan were successfully prepared by a simple solution-evaporation method. Multiwalled carbon nanotubes (MWCNTs) were treated by poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT-PSS) in water before mixed with a chitosan solution to improve the dispersion of MWCNTs and interfacial compatibility between MWCNTs and chitosan. The morphological and mechanical properties of the prepared PEDOT-PSS/MWCNT/chitosan nanocomposites have been characterized with field emission scanning electron microscopy (FESEM) and tensile tests. MWCNTs were observed to be homogeneously dispersed throughout the chitosan matrix. As compared with the neat chitosan, the tensile strength and modulus of the nanocomposite were greatly improved by about 61% and 34%, respectively, with incorporation of only 0.5 wt.% of MWCNTs into the chitosan matrix. The comparison of mechanical properties for PEDOT-PSS/MWCNT/chitosan and pristine MWCNT/chitosan nanocomposites has been made. The hardness of the nanocomposites was also evaluated by nanoindentation.     

Hard-templating synthesis of mesoporous carbon spheres with controlled particle size and mesoporous structure for enzyme immobilization

Mesoporous carbon spheres (MCSs) with controlled particle size and pore structure were synthesized via a combined hard templating and sol–gel processing within water-in-oil emulsions, using resorcinol–formaldehyde polymer as carbon precursor and colloidal silica nanoparticles as hard templates. The addition of silica nanoparticles in polymer sol not only served as the pore structure reagents but also shortened the gelation time, making it easy to control the emulsion process. The sphere size of MCSs can be controlled in the range from 10 to 500 μm by changing the emulsification conditions. The pore structure of MCSs can be tuned by adjusting the mass ratio of resorcinol–formaldehyde polymer to silica nanoparticles and the diameter of silica nanoparticles. The as-prepared MCSs possessed large surface area (>600 m² g⁻¹), large pore volume (>1 cm³ g⁻¹) and a narrow pore size distribution replicated from the silica nanoparticles used. These MCSs exhibited extraordinary high adsorption capacities (ca. 1100 mg g⁻¹) for α-Chymotrypsin (Chy) in solution. Due to their well-developed pore structure and the controllable pore size, as well as the unique shape and good affinity to biomolecules, the as-prepared MCSs should have a good potential in enzyme immobilization.     

In-situ formed graded microporous structure in titanium alloys and its effect on the mechanical properties

A simple method to fabricate porous titanium was developed, with which the graded microporous titanium alloys could be prepared by simply casting. The in-situ formed graded microporous structure and its effect on the mechanical properties of the titanium alloys were investigated. The results indicated that the mechanical properties of such graded microporous titanium alloys were superior to the porous titanium fabricated by other methods. This work provides a bright prospect for the production of graded porous titanium alloys with low-cost and high properties. This method can also be applied to synthesize other porous metallic biomaterials.     

Calcium and potassium addition to facilitate the sintering of bioactive glasses

Nowadays bioactive glasses are diffused in medical practice due to their excellent bioactivity. However high temperature treatments, which are commonly required in several processing routes, may induce the glass to crystallize into a glass-ceramic, with possible negative effects on its bioactivity. In this work a new bioactive glass composition, inspired by the widely used Bioglass® 45 S5, was formulated by increasing the calcium content and substituting the sodium oxide with potassium oxide. The novel glass can be treated at a relatively low temperature (800 °C) and it is characterized by a reduced tendency to crystallize with excellent effects in terms of bioactivity, according to in vitro tests. Therefore, the new composition opens intriguing scenarios whenever a thermal treatment is required to apply or to sinter the glass, such as in the production of scaffolds or the deposition of coatings.     

Peptide and Protein Presenting Materials for Tissue Engineering

Tissue engineering aims to create new tissues and organs to replace those lost to disease, trauma, or congenital defects. However, considerable instruction must be given to the cells forming these new tissues if one is to create a tissue structurally and functionally similar to the native tissue. Materials are ideal for the local presentation of various peptides and proteins that can bind to cell surface receptors and regulate cell function. An overview of techniques to present peptides and proteins from materials, and the utility of these systems in engineering tissues in vitro and in vivo is presented.     

Microstructure evolution of Ti–30Nb–(4Sn) alloys during classical and step-quench aging heat treatments

Recent studies involving step-quench (SQ) heat treatments have shown that, unlike classical quench-and-aging (QA) heat treatments, SQ route can favour precipitation mechanisms that are strongly dependent on decomposition of the parent β-phase. In this work, Ti–30Nb and Ti–30Nb–4Sn (wt-%) alloys were subjected to cold-working, recrystallisation and then to either classical or SQ heat treatments at 400°C. Among QA samples, ω-phase is formed in both alloys during the heating ramp. By the SQ route, we found extensive isothermal ω-phase precipitation in Ti–30Nb during aging. On the other hand, a complete suppression of ω-phase in Ti–30Nb–4Sn was observed, thus, α-phase precipitation could take place improving hardness while still preserving a low elastic modulus.     

Fabrication and Characterization of Multicomponent Polysaccharide/Nanohydroxyapatite Composite Scaffolds

Carrageenan–hyaluronic acid/nanohydroxyapatite/microcrystalline cellulose composite scaffolds with various amounts of microcrystalline cellulose content (from 0 to 60?wt%) were prepared using freeze-drying method. The results showed highly porous (from 94.0?±?1.09 to 85.0?±?1.05%) composite scaffolds with high water-uptake capacity, average pore size ranging 200–650?µm, and improved mechanical properties (in dry and wet states). Additionally, cytocompatibility of composite scaffolds was evaluated by in vitro culture of osteoblast (MC3T3-E1) cells for 1 and 3 days of incubation and demonstrated good cell adhesion, infiltration, and proliferation. Thus, as-obtained composite scaffolds may have promising application in low-loading bone tissue engineering applications.